Acoustical trauma during the sensitive period of postnatal development may result in the impairment of the auditory system, manifested as deteriorated auditory sensitivity and abnormalities in the processing of auditory signals. The acoustic startle refl ex (ASR) and the prepulse inhibition (PPI) of the ASR were examined in 3–6-month-old rats exposed to broad-band noise (125 dB SPL, 8 min) in early postnatal life (day 14). Hearing thresholds in noise-exposed rats, examined by measurements of auditory evoked responses, were found to be normal. The ASR to tones in the range of 2–16 kHz and the PPI of the ASR to a noise burst (110 dB SPL) induced by 2, 4, 8, 12 and 16 kHz tones over a range of 20–80 dB SPL were measured in exposed rats and in age-matched controls. In all exposed rats, a decreased strength of the startle refl ex in response to intense stimuli was observed in comparison with controls. The effect of acoustic trauma on the PPI was different from the effect on the ASR: tones of 20–30 dB SPL were able to suppress the ASR in exposed rats signifi cantly more than in control animals, a similar tendency was observed at higher intensities. The results indicate that acoustic trauma in the early developmental period induces abnormalities in the auditory system of rats in the processing of stimulus intensity in addition to abnormalities in the processing of sound frequency [Grécová et al. (2009) Eur J Neurosci, in press]. Supported by AV0Z50390512, GACR 309/07/1336, LC 554.
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